If you were going to be doing ALOT of HD editing then the i7 will have an advantage over the i5, the main difference is Hyper-Threading, explained below...

Another significant performance difference is how the Core i7 and Core i5 products will be handling hyper-threading. Hyper-threading is a technology used by Intel to simulate more cores than actually exist on the processor. While Core i7 products have all been quad-cores, they appear in Windows as having eight cores. This further improves performance when using programs that make good use of multi-threading.

All Sandy Bridge Core i5 processors have hyper-threading disabled, and all Sandy Bridge Core i7 processors have hyper-threading enabled. This is a major feature difference of Core i5 vs Core i7 processors, and it will give the Core i7 products an advantage over Core i5 processors in some heavily multi-threaded applications.